FIG. 1 shows a schematic cross-sectional view of an encapsulating package of a bolometric detector according to the prior art that is typically used for thermal infrared detection. Package 1 essentially comprises a substrate 2 made, for example, of a ceramic material or metal or even a combination of both these types of materials. This substrate constitutes the base of package 1. It is provided with side walls 3 and the enclosure 4 thus defined is closed off by a cover or lid 5 which, in this case, has a window 6 that is transparent to the wavelength range that is of interest (typically 8-12 micrometers or 3-5 micrometers in the case of infrared imaging).
Package 1 thus defined comprises, inside enclosure 4, a bolometric detector 7 which is located underneath window 6. This bolometric detector, e.g. a two-dimensional retina of microbolometers, is generally produced on the surface of an electronic circuit 8 that forms the wanted signal and which is itself linked to the external environment via a series of low-power inputs/outputs 9, usually by wired connections. These inputs/outputs are connected to the electronics of the system that includes the detector, typically a camera, by usual means of the solder type or by means inserted in a PCB.
Side walls 3 are sealed on substrate 2 and cover or lid 5 is sealed on the upper edge of side walls 3 in a manner which ensures that the pressure inside enclosure 4 is typically less than 10−2 mbar throughout the entire service life of the product. This hermetic sealing is also performed so that the leak rate is typically less than 10−12 mbar 1/s in helium.
Maintenance of this reduced pressure is ensured by means of an element traditionally referred to as a getter 10, i.e. a member that comprises a material capable of absorbing and generally trapping gas molecules that are released during the life of the detecting component and which originate from all the surfaces of the constituents that are in communication with the space inside enclosure 4.
Such a getter material can be solid, i.e. consist of sintered powder having a generally cylindrical shape, possibly with a refractory metal wire passing through it and being used to fix and electrically activate the getter by the Joule effect. The getter may also be deposited by using various methods such as screen printing or Physical Vapor Deposition (PVD) on a preferably metallic support 11 which can, as in the case of solid getters, be used as a means of fixing and electrically connecting the getter. In this case, electrical connection 12 is a high-power input/output in order to enable electrical activation of the getter by the Joule effect.
Such devices according to the prior art are described, for example, in Documents U.S. Pat. No. 7,470,904, U.S. Pat. No. 4,956,554 and U.S. Pat. No. 5,317,157.
Activation of the getter is obtained by increasing the temperature, after enclosure 4 has been exhausted by pumping, of the active getter material to (usually) between 300 and 900° C., depending on the alloy used in the active part of the getter. This temperature increase is obtained by the Joule effect, i.e. by passing an electric current through the resistive metal support or by increasing the temperature of the enclosure of the package, and hence the getter, to the required activation temperature.
Regardless of the package used, getter 10 is fixed inside the latter during a specific step that is separate from the step of fixing the detector and, generally speaking, the other elements that are required in order to assemble the various constituents of the finished component (product). This operation is expensive in terms of tools and materials and also requires a lot of labor.
The object of the present invention is precisely to simplify this operation.